Abrasive device

ABSTRACT

Rotary abrasive members formed of strip-defining sheet material gathered about a hub and having pre-weakened lines defining a plurality of abrasive strips which at the periphery can separate and conform to the work piece.

D United States Patent 1191 011 3,729,872

Hall, Jr. 1 51 May 1, 1973 ABRASIVE DEVICE 3,191,208 6/1965 Churchill ..15/230.17

3,212,819 10/1965 Churchill ..51/40l X lnvemofi 3 Winthrop Hall, Swuale, 3,212,868 l0/1965 Churchill ..51/401 x 38S- [73] Assignee: FT; 8? iloiii iariy, Reckland, Primary Examine"*otheu Simpson M Attorney-John Noel Williams 22 Filed: May 5, 1971 211 Appl.No.: 140,451 [57] ABSTRACT Rotary abrasive members formed of strip-defining [2%] }J.S.(gl 9051/3528, 5l/40l Sheet material gathered about a hub and having pref 1 i "B24d 1 B 4d 11/00 weakened lines defining a plurality of abrasive strips [58] Field of Search ..51/358, 376-378, which at the periphery can separate and conform to 51/401,394, 365,293; 15/181, 230.17 the Work piem [56] References Cited UNITED STATES PATENTS 22 Claims, 13 Drawing Figures 9/1957 Schaffner ..51/376 71 ll I 1 59b 590/ 58b 58c! I6 58 1 Pmilied May 1, 1973 3,729,372 I 3 Sheets-Sheet 1 v FIG 2 [Hill Patented May1,1973 3,729,872

3 Sheets-Sheet 2 ABRASIVE DEVICE This invention relates to abrasive devices, and particularly to flexible, rotary devices having a peripheral working surface adaptable to contoured surfaces.

To achieve desirable abrasive qualities and contour conformability without sacrificing worklife, abrasivedevices must combine rigid abrasive grain anchoring for sure cut with a flexible macrostructure for working contours. Flexible-cg, foam-substrates provide sufficient flexibility, but also have, of necessity, flexible grain anchoring, and hencereduced cutting abilities.

One prior attempt to make flexible abrasive devices from coated abrasive substrates involves assembling a plurality of discrete. individual coated abrasive members in parallel about a central hub, in the manner of a paddle wheel or flap wheel with the abrasive coated surfaces oriented to approach the workpiece facing it. However, in use, the individual abrasive members or leaves of the flap-wheel tend to gang up or bunch as the leaves contact a work surface, and suddenly swing by the workpiece together, leaving an uneven mackrelled" surface on the workpiece, and resulting in ,uneven wearing of the wheel. Also, assembling a number of modular" wheels so formed in parallel to provide different widths is impractical because the edges of adjacent wheels will interface insufficiently to avoid unworked lines in the workpiece at the interfacehence, such flap-wheels can be made only in custom widths. Further such devices are slow to assemble, since a large numberhundredsofindividual abrasive leaves must be assembled to a hub.

Another attempt involves providing, again, a plurality of abrasive sheets, each sheet having a central opening and being torn along a number of parallel lines extending partway from each of two opposite edges toward the center to provide a plurality of strips. A large number of the sheets are laid on top of one another, concentrically, but offset a few degrees from other sheets, so that the outer edges of each sheet are prising a substrate and an abrasive-coating on at least one side of the substrate; the material extends in a circumferential direction and is gathered about the hub along an are having a circumferential dimension which is substantially smaller than the ungathered extent of the material; and the gathered material has a plurality of spaced apart, substantially radially extending preweakened lines defining a plurality of strips, the outer peripheral portions of the strips being separable from each other during operation to definecollectively at the outer edge of the membera conformable and effecarranged generally within a circle, and are secured at otherwise finishing objects, both metal (ferrous and non-ferrous) and non-metal, having contoured or otherwise irregular surfaces such as castings, automotive parts, welded fabrications such as metal tables,

cabinets, furniture, and the like.

Another object is to provide a simple, economical and versatile method for making abrasive devices of various widths, flexibilities, and cutting properties, and particularly devices having substantially uniform cutting properties across their width.

One aspect of the invention features a rotary abrasive member comprising a supporting hub, and abrasive strip-defining sheet material, the sheet material comtive abrasive working surface.

Proposed embodiments of the invention feature:

a strip defining sheet of material which extends circumferentially about the hub, and in its other direction extends from the outer periphery of the abrasive member, inwardly to the hub and back to the periphery, the portion of the sheet adjacent the hub being secured thereto and each of the two peripheral portions of the sheet providing a series of abrasive strips which are separable from other strips in the series during operation; the just mentioned abrasive member in which the sheet material has an abrasive coating on only one side of the substrate, the material being folded upon itself to define the two peripheral portions with the abrasive coating of the two portions facing outwardly in opposite axial directions; the abrasive member wherein the portion of the sheet adjacent the hub has radially-extending lines of weakness along which the material is folded in its gathered state; the just mentioned abrasive member including opposed, interlocked series of gripping teeth securing the sheet material tothe hub, the sheet material being partially captured along some of said lines of weakness in the region of said teeth; the abrasive member wherein the sheet material has an abrasive-coating on only one side of the substrate, the opposite side of the substrate being uncoated, the sheet material having less resistance to bend in the direction of the uncoated side than in the opposite direction; the abrasive member wherein adjacent pre-weakened lines extend in parallel in the ungathered sheet material; the abrasive member wherein the pre-weakened lines comprise alternating areas of greater and lesser strength so that said material has a tendency to rupture incrementally along said lines; this construction wherein a pre-weakened line comprises a series of areas of weakened material spaced apart by portions of unweakened material, and this construction wherein the areas of weakened material are defined by surface cuts extending from one side of said sheet partially through the thickness of the sheet or wherein the areas of weakened material are defined by cuts extending completely through said sheet;

the abrasive member wherein the areas of weakened material are elongated and have a major dimension extending along said line;

the abrasive member wherein the sheet material is ruptured along a substantial number of the preweakened lines adjacent the working surface to define at the working surface a substantial number of elongated individual abrasive strip portions unconnected to circumferentially adjacent portions of the sheet material, in regions of the sheet material located radially inwardly there being connections across the pre weakened lines between circumferentially adjacent portions of the sheet;

the abrasive member wherein it is of overall disc form and portions of the material located radially inwardly of the periphery of the member have abrasivecoated sides facing predominantly in the axial direction of the member, while the peripheral portion of the majority of the separated strips are relatively turned, to have a component of the abrasive surface facing in the direction of rotation of the member;

the abrasive member wherein the abrasive-coated sides of the majority of the strips face at an angle less than 90 to the direction of movementof said abrasive member;

the abrasive member wherein the major number of the separated portions of the strips have a separated length of at least three-sixteenth inch;

the abrasive'member wherein the strips have a width to thickness ratio of at least 3;

the abrasive member wherein the sheet material comprises a textile fabric substrate on which there are bonded on one side a distribution of rigid abrasive grains by a suitable bonding material; and

the abrasive member wherein the member includes a plurality of radial pleats with the folds of the pleats located at certain of the pre-weakened lines.

According to another aspect of the invention there is featured a rotary abrasive member comprising a supporting hub and abrasive strip-defining sheet material comprising a substrate and an abrasive coating on a side of the substrate, the material extending circumferentially and being gathered about the hub along an are having a circumferential dimension which is substantially smaller than the ungathered extent of the material, the outer periphery of the gathered material being separated into a multiplicity of generally radially extending abrasive strips, these strips being free to turn relative to each other and relative to inner portions of the sheet from which the strips integrally extend.

And according to another aspect of the invention there is featured a method for making a rotary abrasive member comprising the steps of providing abrasive sheet material having two opposite parallel edges, the sheet material having an abrasive coated side and being pre-weakened along a plurality of preformed parallel weakened zones perpendicular and adjacent to said opposed edges, arranging the sheet material with the abrasive-coated side down about the peripheral surface of a cylindrical support having an annular opening over which the material lies,

drawing the sheet material lying over this annular opening radially into the opening to arrange the sheet material about a circular arc of substantially smaller diameter than the diameter of said support, and

fastening the sheet material so drawn at the circular region, thus to provide an abrasive member comprised at its periphery of Strip-forming material. Preferred embodiments of this method feature the diameter of the support being at least two times the diameter of the circular arc, and the sheet material comprising a plurality of overlapped sheet members arranged about the support.

Other objects, features and advantages will occur to one skilled in the art from the following description ofa preferred embodiment of the invention, taken along with the attached drawings thereof, in which:

FIG. 1 is a perspective view of an abrasive member embodying the present invention;

FIG. 2 is an elevational view of a coated abrasive sheet used to form the member of FIG. 1;

FIG. 3 is a sectional view of apparatus useful in forming the abrasive member of FIG. 1;

FIG. 4 is an elevational view of an alligator ring" useful in the abrasive member of FIG. 1;

FIG. 5 is a sectional view of the ring of FIG. 4;

FIG. 6 is a sectional view of the abrasive member of FIG. 1,.taken along a radius thereof;

FIG. 7 is a somewhat idealized elevational view of radially separated portions of an abrasive member embodying the present invention, illustrating structural formations occurring therein; FIG. 7a is a view similar to FIG. 7 on a considerably enlarged scale; and

FIGS. 8a-8e show a series of sectional, somewhat diagrammatic views of various structural formations of FIG. 7, as indicated therein at the lines 8a-8e.

The figures show an abrasive member 10 formed of a hub 12 which has a mounting disc 14 and an alligatortype lacing ring 16, and abrasive coated sheet material 18, having a coated side 18a and an uncoated side 18b.

The construction of this member is best illustrated by referring to FIGS. 3 to 6. FIG. 2 shows a starting abrasive sheet 20, which has abrasive grains (preferably 60 grit or finer) adhered to one side of a substrate (cloth,

paper or the like) by an appropriate resin. The substrate is preferably a woven jean (J-weight) or drill (X-weight). The sheet has opposed parallel edges 22 and, running perpendicular thereto, a plurality of parallel scored or pre-weakening lines 24, along which the sheet will preferably rupture when a shear force is applied. The sheet illustrated is a stagger-scored abrasive sheet, with a number of scores 28 formed through the resin-abrasive coating into, but not necessarily completely through the substrate. The scores of adjacent zones 24a, 24b are staggered, so as to provide a sheet of uniform strength in the direction a, while allowing localized ruptures at the scores, or along the entire weakened zones defined by the scores. The illustrated sheet is a heavy drill cloth, coated with a resin (e.g., phenol-formaldehyde resin, animal glue, etc.),

220 grit aluminum oxide abrasive grains, and overcoated with resin (phenol-formaldehyde), available from Norton Co. under the trade name Resinall Metallite Cloth 220, X Weight. The zones 24 are onefourth inch apart (preferably at least one-sixteenth inch apart) and scores 28 are each 52 inch long, are separated from the next score of the zone by one-eighth inch, and do not entirely pierce through the substrate.

The overall thickness of the illustrated sheet is approximately 0.020 inch.

As shown in FIG. 3, a number of sheets 20 were held side by side in a circumferential array with the abrasive-coated side down against the periphery of a split drum 34, this drum having a wide annular opening 36. (As an alternative, continuous sheets extending fully about the drum may be employed.) The edges 22 of each sheet were equidistant from the opening 36, with the scoring lines lying parallel to the axis of the drum.

A smaller diameter ring 16 was supported within the annular opening 36. As shown in FIGS. 4 and 5, this ring has teeth 44. A force, F, was then applied around the periphery of the drum-formed sheets pushing them into the opening 36, and thus condensing the sheets, while folding the sheets back upon themselves, abrasivecoated side facingaxially outwardly on opposite sides until the mid portions of the sheets were condensed to the ring 16. The teeth 44 were then clamped toward each other to hold the gathered material, as shown in FIG. 6. The finished abrasive member 10, was of disc form and had an outer diameter of about 16 inch and an average effective thickness of about onehalf inehi.e., when rotated in contact with a workpiece, the device had an effective peripheral abrasive working surface about /2 inch wide.

In the immediate vicinity of the hub where the rela tively rigid abrasive sheet is gathered to greatest compression the scoring or predetermined lines of weakness enable the uniform gathering without gross bulges. The pleats and folds follow these lines and in places rupture can occur along the lines to facilitate the closing of the teeth.

Although the abrasive member as illustrated was formed by condensing, other gathering methods could also be employed, such as pleating the abrasive sheets and gathering one pleated edge on a rotating gear wheel or other take up device. Or, such a gathered pleated material might be helically wound to form members of multiple-sheet thickness.

Referring to FIGS. 1, 7 and 7a, the resultant abrasive member 10 has a plurality of radially extending weakened lines 24, which, prior to rotating the member against a workpiece, may all or substantially all be unruptured. A number of pleats 45 are formed along some but not necessarily all of the lines 24, the pleats gradually flattening in a radially outward direction to accommodate the gradually lesser gathering of material in that direction.

FIGS. 7 and 7a show a portion of the abrasive member of FIG. 1, after the member has been conditioned" by rotating it against a workpiece (located about one-fourth to one-half inch from the center of the member, for perhaps I to 5 minutes at a speed of 1,000 to 2,000 rpm). As a result of this conditioning the weakened lines at the periphery are ruptured providing radially extending abrasive strips. It will be apparent from what follows that the workpiece location, and speed and time ofconditioning rotation are dependent on the flexibility desired in the finished member (the longer the separated strips the more flexible), which in turn depends upon the use to which the member is to be putthe curvature of contours to be worked, the amount and speed of cut desired, and the like.

FIGS. 7 and 8 illustrate the random orientation of the abrasive sheets in a conditioned abrasive member, and shows, in particular, several illustrative abrasive sheet portions or groups of abrasive strips 50, 52, 54, 56 and 58. The arrow 60 indicates the rotational direction of the wheel. Group 50 includes three strips 50a, 50b, 500, of which the abrasive-coated surface of strip 5011 faces the working direction of the abrasive member where secured to ring 16, the abrasive-coated surface of strip 50b is at about a 180 angle to the working direction where secured to ring 16, and the abrasive coated surface of strip 500 faces away from the working direction where secured to the ring-Lea, has its non-coated sur face facing the working direction, The tips of each strip, however, face the working direction, the tip of strip 50a being almost exactly normal to the working direction, and those of strips b and 500 being at acute angles to the working direction. Moreover, the weakened zones 51a, 5117 have ruptured adjacent the tip ends of the strips, rendering the tips of the strips able to flexibly distort or bend back when they engage a workpiece (as do the strips shown in FIG. 7 engaging the workpiece 100), to engage surface contours, to the extent or partly to the extent of the ruptures at .weakened lines 51a, 51b. Yet the radially innerregions of the strips remain interconnected across the unruptured portions of zones 51a, 5112, thus providing a firmer support for the abrading tips, for rapid, uniform cutting. Moreover, the sheet material forming the strip being itself a heavy, rigid, sandpaper-like material, the strips, even where separated, have sufficient stiffness to efficiently abrade workpiece portions not requiring the leaves to be bent back to the full extent of the ruptures.

The group 52 has two strips, of which strip 52a has its abrasive-coated surface facing the working direction along its entire length, whereas the base of strip 52b, at ring 16, has its abrasive-coated surface facing in a direction opposite to the working direction. Yet, the rupture of weakened zone 53 between the strips, permits strip 520 to twist substantially more than 90 between its base and its tip, so that the tip has abrasivecoated surface facing, at an acute angle, the working direction.

Group 54 includes six strips, of which the abrasivecoated side of strip 54a faces in the working direction at an acute angle along its entire length; the abrasivecoated side of strip 54!) falls away from the working direction at its base but gradually twists to face the working direction at a gradually increasing angle toward its tip; the abrasive-coated side of strip 54c undergoes a serpentine twist, being about parallel to the working direction at the base of the strip, facing away from it in intermediate regions, and returning to face in the working direction at its tip; the abrasive coated surface of strip 54!) faces opposite the working direction I base, but twists to face in the working direction at an acute angle thereto at its tip; and, the abrasive coated surface of strip 54e twists from an angle almost normal to the working direction at its base to an angle barely acute to, but still facing in the working direction at its tip.

Group 54 further illustrates the effect of staggered scoring, the ruptures of weakened zones 55a and 55c being substantially deeper than the ruptures of zones 55!) and 55d.

Group 56 illustrates a strip 56!; which has its abrasive-coatcd surface at all times facing away from the working direction, whereas the abrasive-coated surface of strip 56a-faces in the working direction through its entire extent.

In group 58, neither strip 5811 nor strip 58b hasits abrasive-coated side facing in the working direction and, notably, the weakened zone 59a therebetweenhas remained unruptured, whereas the strip 580, separated from strip 58h by a ruptured weakened zone 5%, has its abrasive-coated side facing in the working direction at its tip, even though the abrasive-coated side, at the base, is facing away from the working direction.

The resultant working surface, as seen in FIG. 7 as it would be against a workpiece 100, is in the form of a plurality of overlapping strips, over 50'percent of which (even up to 75 percent of which) face their abrasive towards the workpiece, and these successively wipe and abrade the workpiece as the member is rotated. Because of the interconnection between adjacent strips at the radially inward areas of the strips, bunching up of the strips about the circumference is avoided, whereas the rupture at the tips of the strips make the abrasive member quite flexible. It is believed that the surprising number of forward-facing abrasive surfaces, far in excess of what might be expected, is due to the difference in flexibility between the coated and uncoated sides of the abrasive sheet. Because the noncoated side is more readily deflected than is the rigid resin-abrasive coated side, the sheet preferably bends or curls toward its uncoated side. Thus, considering two adjacent strips, which in formation contains along the weakened line therebetween a pleat so that their uncoated sides face toward one another, and the coated side of only one faces in the working direction, as an initial conditioning force is applied, the forward facing strip will tend to bend backward, toward its uncoated side. The resistance to bending of the adjacent rearward-facing strip, however, will result in a shearing force being applied along the weakened zone between the strips, causing the tips of the strips to separate. The rearward-facing strip will then be free to twist so that its tip can turn to face the workpiece, thus absorbing the conditioning forces in the preferred bending mode. Of course, not all strips will so turn, but it has been found that up to one-half of the strips facing rearwardly on formation are conditioned to face forward after moderate conditioning. Particularly preferred coated abrasive for so twisting is that which has been triple flexed by running the abrasive, when formed, over a series of angled rollers. Additional curling toward the uncoated side may be promoted by steaming the abrasive sheet prior to gathering or after partial working or conditioning. Where the substrate is coated on both sides, preferred flexibility or curling can be promoted by providing, e.g., a more flexible coating or a thinner coating, or less abrasive on one side than on the other. The rupturing is controlled, however, by the conditioning forces and by the gathered construction itself. The closer one comes to the center of the abrasive material, the greater becomes the density of gathered material, and hence the greater the tendency of the material to resist working forces. Hence, the tendency to flex is reduced, and so also are the shear forces along the weakened zones. The flexibility may also be enhanced by preslashing large numbers of the ruptured zones prior even to conditioning, so that the ruptures extend to greater depths than would normally be achieved by conditioning the member against a workpiece.

Of course, even where the uncoated side of the strip faces the workpiece, since abrading takes place at the tip and edge of the strip, the strip will do some abrading.

The individual wheels are rapidly and economically assembled, such as by the heretofore described preferred condensing".procedure. Also, two or more abrasive members 10 can be combined, in modular fashion, to provide wheels of greater width, and yet, because of the irregular peripheral edges of the working surface of each wheel, and the individual flexibility of the abrasive strips, the resultant working surface of the combined wheels will be as uniform across its width as that of one wheel. Where members are so combined, a workpiece can also be arranged to enter the abrasive members from the side (i.e., to travel generally parallel to the axis of the members) and pass along successive members, the succeeding members perhaps being constructed with a decreasing coarseness of grain to accomplish a continuous cut and finishing operation.

Such abrasive members are particularly useful for abrading-finishing or polishing-unusually contoured surfaces such as a brass (sand-casted) J bend pipe used in traps under sinks. The inside bend of a l-inch diameter pipe, bent into a J with 3 inch between centers of the two J" surfaces, was abraded using a l-inch abrasive wheel (two abrasive members 10 secured in parallel), at 1,100 r.p.m. for about 4-5 minutes. At higher speeds, more cutting (more stock removal) is accomplished, but with less flexibility. Such .l-bends have been previously smoothed from their mottled sand-cast condition only by using a combination of an abrasive compound and a rotary abrasive tool. Highly contoured pieces such as valves, fittings, door-knobs, door-knob rosettes, saber-saw housings, intricate aluminum die-castings and other problem pieces can all be rapidly, efficiently and smoothly polished and smoothed by such abrasive members as described.

In lieu of or in addition to the described scored sheets, pre-weakened lines may also be established by cutting through the sheet at one or more spaced intervals, or serrating, or punching, the extent of the cuts or scores and the uncut or unscored spaces therebetween being determined in accordance with desired properties for the finished abrasive device.

Other embodiments will occur to those skilled in the art and are within the following claims.

What is claimed is: I l. A rotary abrasive member comprising a supporting hub, and abrasive strip-defining sheet material,said sheet material comprising a substrate'and an abrasivecoating on at least one side of said substrate, I

said material extending in a circumferential direction and being gathered about said hub along an arc,

said gathered material having a plurality of spaced apart, substantially radially extending preweakened lines defining a plurality of strips, the outer portions of said strips being separable from each other during operation to define collectively at the outer edge of said member a conformable and effective abrasive working surface.

2. The rotary abrasive member of claim 1 wherein a strip-defining sheet of said material which extends circumferentially about said hub, in its other direction extends from the outer periphery of said abrasive member, inwardly to said hub and back to the periphery, thereby defining two outer peripheral portions of said sheet, the portion of said sheet adjacent said hub being secured thereto and each of the two peripheral portions of said sheet providing a series of abrasive strips which are separable from other strips in the series during operation.

3. The abrasive member of claim 2 wherein said sheet material has an abrasive-coating on only one side of said substrate, the material being folded upon itself to define 'said two peripheral portions with the abrasive coating of said two portions facing outwardly in opposite axial directions.

4. The abrasive member of claim 1 wherein the portion of said sheet adjacent said hub has radially-extending lines of weakness along which said material is folded in its gathered state.

S. The abrasive member of claim 4 wherein said hub includes opposed, interlocked gripping teeth securing said sheet material to said hub, said sheet material being partially ruptured along some of said lines of weakness in the region of said teeth.

6. The abrasive member of claim 1 wherein said sheet material has an abrasive-coating on only one side of said substrate, the opposite side of said substrate being uncoated, said sheet material having less resistance to bend in the direction of said uncoated side than in the opposite direction.

7. The abrasive member of claim 1 wherein adjacent pre-weakened lines extend in parallel in the ungathered sheet material.

8. The abrasive member of claim 1 wherein said preweakened lines comprise alternating areas of greater and lesser strength so that said material has a tendency to rupture incrementally along said lines.

9. The abrasive member of claim 8 wherein a said pre-weakened line comprises a series of areas of weakened material spaced apart by portions of unweakened material.

10. The abrasive member of claim 9 wherein said areas of weakened material are defined by surface cuts extending from one side of said sheet partially through the thickness of said sheet.

11. The abrasive member of claim 9 wherein said areas of weakened material are defined by cuts extending completely through said sheet.

12. The abrasive member of claim 9 wherein said areas of weakened material are elongated and have a major dimension extending along said line.

13. The abrasive member of claim 1 wherein said sheet material is ruptured along a substantial number of said pre-weakened lines adjacent said working surface to define at said working surface a substantial number of elongated individual abrasive strip portions unconnected to circumferentially adjacent portions of said sheet material in regions of said sheet material located radially inwardly there being connections across said pre-weakened lines between circumferentially adjacent portions of said sheet.

14. The abrasive member of claim 13 wherein it is of overall disc form and portions of said material located radially inwardly of the periphery of said member having abrasive coated sides facing predominantly in the axial direction of said member, while the peripheral portion of the majority of said separated strips are relatively turned, to have a component of the abrasive surface facing in the direction of rotation of said member.

15. The abrasive member of claim 13 wherein the abrasive-coated sides of the majority of said strips face at an angle less than to the direction of movement of said abrasive member.

16. The abrasive member of claim 13 wherein the major member of said strips have a separated length of at least three-sixteenth inch.

17. The abrasive member of claim 1 wherein said stri%s have a width to thickness ratio of at least 3.

1 The abrasive member of claim 1 wherein said sheet material comprises a textile fabric substrate having a distribution of rigid abrasive grains bonded to a side thereof.

19. A rotary abrasive member comprising a supporting hub and abrasive strip-defining sheet material comprising a substrate and an abrasive coating on a side of said substrate, said material extending circum ferentially and being gathered about said hub along an arc, the outer periphery of said gathered material being separated into a multiplicity of generally radially extending abrasive strips, said strips being free to turn relative to each other and to inner portions of said sheet from which said strips integrally extend.

20. A method for making a rotary abrasive member comprising the steps of providing abrasive sheet material having two opposite substantially parallel edges, the sheet material having an abrasive coating on at least one side and being pre-weakened along a plurality of preformed substantially parallel weakened zones perpendicular and adjacent to said opposed edges, arranging the sheet material with an abrasivecoated side down about the peripheral surface of a cylindrical support having an annular opening over which said material lies, drawing said sheet material lying over said annular opening radially into said opening to arrange said sheet material about a circular arc of substantially smaller diameter than the diameter of said support, and fastening said sheet material so drawn at said circular region, to provide an abrasive member comprised at its periphery of strip-forming material.

21. The method of claim 20 wherein the diameter of said support is at least two times the diameter of said circular arc.

22. The method of claim 20 wherein said sheet material comprises a plurality of overlapped sheet members arranged about said support. 

1. A rotary abrasive member comprising a supporting hub, and abrasive strip-defining sheet material, said sheet material comprising a substrate and an abrasive-coating on at least one side of said substrate, said material extending in a circumferential direction and being gathered about said hub along an arc, said gathered material having a plurality of spaced apart, substantially radially extending pre-weakened lines defining a plurality of strips, the outer portions of said strips being separable from each other during operation to define collectively at the outer edge of said member a conformable and effective abrasive working surface.
 2. The rotary abrasive member of claim 1 wherein a strip-defining sheet of said material which extends circumferentially about said hub, in its other direction extends from the outer periphery of said abrasive member, inwardly to said hub and back to the periphery, thereby defining two outer peripheral portions of said sheet, the portion of said sheet adjacent said hub being secured thereto and each of the two peripheRal portions of said sheet providing a series of abrasive strips which are separable from other strips in the series during operation.
 3. The abrasive member of claim 2 wherein said sheet material has an abrasive-coating on only one side of said substrate, the material being folded upon itself to define said two peripheral portions with the abrasive coating of said two portions facing outwardly in opposite axial directions.
 4. The abrasive member of claim 1 wherein the portion of said sheet adjacent said hub has radially-extending lines of weakness along which said material is folded in its gathered state.
 5. The abrasive member of claim 4 wherein said hub includes opposed, interlocked gripping teeth securing said sheet material to said hub, said sheet material being partially ruptured along some of said lines of weakness in the region of said teeth.
 6. The abrasive member of claim 1 wherein said sheet material has an abrasive-coating on only one side of said substrate, the opposite side of said substrate being uncoated, said sheet material having less resistance to bend in the direction of said uncoated side than in the opposite direction.
 7. The abrasive member of claim 1 wherein adjacent pre-weakened lines extend in parallel in the ungathered sheet material.
 8. The abrasive member of claim 1 wherein said pre-weakened lines comprise alternating areas of greater and lesser strength so that said material has a tendency to rupture incrementally along said lines.
 9. The abrasive member of claim 8 wherein a said pre-weakened line comprises a series of areas of weakened material spaced apart by portions of unweakened material.
 10. The abrasive member of claim 9 wherein said areas of weakened material are defined by surface cuts extending from one side of said sheet partially through the thickness of said sheet.
 11. The abrasive member of claim 9 wherein said areas of weakened material are defined by cuts extending completely through said sheet.
 12. The abrasive member of claim 9 wherein said areas of weakened material are elongated and have a major dimension extending along said line.
 13. The abrasive member of claim 1 wherein said sheet material is ruptured along a substantial number of said pre-weakened lines adjacent said working surface to define at said working surface a substantial number of elongated individual abrasive strip portions unconnected to circumferentially adjacent portions of said sheet material in regions of said sheet material located radially inwardly there being connections across said pre-weakened lines between circumferentially adjacent portions of said sheet.
 14. The abrasive member of claim 13 wherein it is of overall disc form and portions of said material located radially inwardly of the periphery of said member having abrasive coated sides facing predominantly in the axial direction of said member, while the peripheral portion of the majority of said separated strips are relatively turned, to have a component of the abrasive surface facing in the direction of rotation of said member.
 15. The abrasive member of claim 13 wherein the abrasive-coated sides of the majority of said strips face at an angle less than 90* to the direction of movement of said abrasive member.
 16. The abrasive member of claim 13 wherein the major member of said strips have a separated length of at least three-sixteenth inch.
 17. The abrasive member of claim 1 wherein said strips have a width to thickness ratio of at least
 3. 18. The abrasive member of claim 1 wherein said sheet material comprises a textile fabric substrate having a distribution of rigid abrasive grains bonded to a side thereof.
 19. A rotary abrasive member comprising a supporting hub and abrasive strip-defining sheet material comprising a substrate and an abrasive coating on a side of said substrate, said material extending circumferentially and being gathered about said hub along an arc, the outer periphery of said gathered material being separated into a multiplicity of generally radially extending abrasive strips, said strips being free to turn relative to each other and to inner portions of said sheet from which said strips integrally extend.
 20. A method for making a rotary abrasive member comprising the steps of providing abrasive sheet material having two opposite substantially parallel edges, the sheet material having an abrasive coating on at least one side and being pre-weakened along a plurality of preformed substantially parallel weakened zones perpendicular and adjacent to said opposed edges, arranging the sheet material with an abrasive-coated side down about the peripheral surface of a cylindrical support having an annular opening over which said material lies, drawing said sheet material lying over said annular opening radially into said opening to arrange said sheet material about a circular arc of substantially smaller diameter than the diameter of said support, and fastening said sheet material so drawn at said circular region, to provide an abrasive member comprised at its periphery of strip-forming material.
 21. The method of claim 20 wherein the diameter of said support is at least two times the diameter of said circular arc.
 22. The method of claim 20 wherein said sheet material comprises a plurality of overlapped sheet members arranged about said support. 